1IO_SUBMIT(2) Linux Programmer's Manual IO_SUBMIT(2)
2
6 io_submit - submit asynchronous I/O blocks for processing
7
9 #include <linux/aio_abi.h> /* Defines needed types */
10 int io_submit(aio_context_t ctx_id, long nr, struct iocb **iocbpp);
12 Note: There is no glibc wrapper for this system call; see NOTES.
14
16 The io_submit() system call queues nr I/O request blocks for processing
17 in the AIO context ctx_id. The iocbpp argument should be an array of
18 nr AIO control blocks, which will be submitted to context ctx_id.
19 The iocb (I/O control block) structure defined in linux/aio_abi.h
21 defines the parameters that control the I/O operation.
22 #include <linux/aio_abi.h>
24 struct iocb {
26 __u64 aio_data;
27 __u32 PADDED(aio_key, aio_rw_flags);
28 __u16 aio_lio_opcode;
29 __s16 aio_reqprio;
30 __u32 aio_fildes;
31 __u64 aio_buf;
32 __u64 aio_nbytes;
33 __s64 aio_offset;
34 __u64 aio_reserved2;
35 __u32 aio_flags;
36 __u32 aio_resfd;
37 };
38 The fields of this structure are as follows:
40 aio_data
42 This is an internal field used by the kernel. Do not modify
43 this field after an io_submit(2) call.
44 aio_key
46 This is an internal field used by the kernel. Do not modify
47 this field after an io_submit(2) call.
48 aio_rw_flags
50 This defines the R/W flags passed with structure. The valid
51 values are:
52 RWF_HIPRI
54 High priority request, poll if possible
55 RWF_DSYNC
57 Write operation complete according to requirement of syn‐
58 chronized I/O data integrity. See the description of the
59 flag of the same name in pwritev2(2) as well the descrip‐
60 tion of O_DSYNC in open(2).
61 RWF_SYNC
63 Write operation complete according to requirement of syn‐
64 chronized I/O file integrity. See the description of the
65 flag of the same name in pwritev2(2) as well the descrip‐
66 tion of O_SYNC in open(2).
67 RWF_NOWAIT
69 Don't wait if the I/O will block for operations such as
70 file block allocations, dirty page flush, mutex locks, or
71 a congested block device inside the kernel. If any of
72 these conditions are met, the control block is returned
73 immediately with a return value of -EAGAIN in the res
74 field of the io_event structure (see io_getevents(2)).
75 aio_lio_opcode
77 This defines the type of I/O to be performed by the iocb struc‐
78 ture. The valid values are defined by the enum defined in
79 linux/aio_abi.h:
80 enum {
82 IOCB_CMD_PREAD = 0,
83 IOCB_CMD_PWRITE = 1,
84 IOCB_CMD_FSYNC = 2,
85 IOCB_CMD_FDSYNC = 3,
86 IOCB_CMD_NOOP = 6,
87 IOCB_CMD_PREADV = 7,
88 IOCB_CMD_PWRITEV = 8,
89 };
90 aio_reqprio
92 This defines the requests priority.
93 aio_filedes
95 The file descriptor on which the I/O operation is to be per‐
96 formed.
97 aio_buf
99 This is the buffer used to transfer data for a read or write
100 operation.
101 aio_nbytes
103 This is the size of the buffer pointed to by aio_buf.
104 aio_offset
106 This is the file offset at which the I/O operation is to be per‐
107 formed.
108 aio_flags
110 This is the flag to be passed iocb structure. The only valid
111 value is IOCB_FLAG_RESFD, which indicates that the asynchronous
112 I/O control must signal the file descriptor mentioned in
113 aio_resfd upon completion.
114 aio_resfd
116 The file descriptor to signal in the event of asynchronous I/O
117 completion.
118
120 On success, io_submit() returns the number of iocbs submitted (which
121 may be less than nr, or 0 if nr is zero). For the failure return, see
122 NOTES.
123
125 EAGAIN Insufficient resources are available to queue any iocbs.
126 EBADF The file descriptor specified in the first iocb is invalid.
128 EFAULT One of the data structures points to invalid data.
130 EINVAL The AIO context specified by ctx_id is invalid. nr is less than
132 0. The iocb at *iocbpp[0] is not properly initialized, or the
133 operation specified is invalid for the file descriptor in the
134 iocb.
135 ENOSYS io_submit() is not implemented on this architecture.
137
139 The asynchronous I/O system calls first appeared in Linux 2.5.
140
142 io_submit() is Linux-specific and should not be used in programs that
143 are intended to be portable.
144
146 Glibc does not provide a wrapper function for this system call. You
147 could invoke it using syscall(2). But instead, you probably want to
148 use the io_submit() wrapper function provided by libaio.
149 Note that the libaio wrapper function uses a different type (io_con‐
151 text_t) for the ctx_id argument. Note also that the libaio wrapper
152 does not follow the usual C library conventions for indicating errors:
153 on error it returns a negated error number (the negative of one of the
154 values listed in ERRORS). If the system call is invoked via
155 syscall(2), then the return value follows the usual conventions for
156 indicating an error: -1, with errno set to a (positive) value that
157 indicates the error.
158
160 io_cancel(2), io_destroy(2), io_getevents(2), io_setup(2), aio(7)
161
163 This page is part of release 4.15 of the Linux man-pages project. A
164 description of the project, information about reporting bugs, and the
165 latest version of this page, can be found at
166 https://www.kernel.org/doc/man-pages/.
167Linux 2017-09-15 IO_SUBMIT(2)